1. Field of the Invention
The present invention relates to a magnetic sensor, in particular a metallic surface identifying sensor, which detects an uneven shape on a surface of a metallic body.
The present invention also relates to a differential magnetism sensor apparatus in which the magnetic variation in a magnetizing coil caused by an object to be detected which generates a magnetic flux in a closed loop is amplified and output. In particular, the present invention relates to a signal processing method for a signal output from a differential detecting coil.
In addition, the present invention relates to a coin identifying apparatus and a magnetic sensor body. More specifically, the present invention relates to improvement in the configuration of an identifying sensor which identifies the authenticity of coins in a vending machine and the like.
Also, the present invention relates to a displacement sensor which detects a relative position in relation to an object to be detected.
Furthermore, the present invention relates to a proximity sensor which detects magnetically the location of an object to be detected without touching the object.
2. Related Art
A coin discriminating machine of an automatic vending machine which makes a distinction between the absence and presence of a coin and between types of coins and a card discriminating machine which makes a distinction between the absence and presence of a magnetic card and between types of magnetic cards both have a magnetism sensor apparatus on board. One type of magnetism sensor apparatus is a differential magnetism sensor apparatus which differentially detects a variation caused by an object to be detected in a magnetic flux which passes through a magnetizing coil, and is disclosed in Tokuhyo No. H7-506687 and Kokai No. H3-162688.
Tokkai S53-42985 discloses a magnetic sensor, in particular a metallic surface identifying sensor, which enables highly precise identification with a simple configuration by using a change in magnetic fluxes. Herein, as shown in FIG. 1, a pair of magnetic pole portions for detection 1 and 2 move while facing the surface to be identified 3a of metallic body 3 having an uneven shape wherein detecting coils 4 and 5 are wound around magnetic pole portions 1 and 2, respectively. Additionally, magnetizing coil 7 is wound around support magnetic pole portion 6 between the pair of detecting magnetic pole portions 1 and 2. When magnetic fluxes 1 and 2 are generated in detecting magnetic pole portions 1 and 2 by an electric flow in magnetizing coil 7, detection signals corresponding to magnetic fluxes 1 and 2 are sent out from detecting coils 4 and 5, respectively.
In the above case, eddy currents are generated on the surface to be identified 3a of metallic body 3 based on magnetic fluxes 1 and 2 such that the eddy currents restrict magnetic fluxes 1 and 2. The eddy currents correspond to the distance between the surface to be identified 3a as a front surface of metallic body 3 and magnetic pole portions for detection 1 and 2. In other words, when surface 3a is flat, both magnetic poles 1 and 2 are at the same distance from surface 3a such that the amounts of magnetic fluxes 1 and 2 to be restricted are identical. As a result, detecting coils 4 and 5 send out output signals of the same intensity. Therefore, a differential output by detecting coils 4 and 5 is maintained at zero.
In the case of the surface to be identified 3a of metallic body 3 having an uneven shape, the distance between magnetic pole portions for detection 1 and 2 and surface 3a continually increases or decreases according to the uneven shape on surface 3a during the shift. Consequently, eddy currents generated on surface 3a change according to a change in the distance. More specifically, when magnetic pole portion 1, which precedes to magnetic pole portion 2 on the right side in FIG. 1, faces convex portion 3b of surface 3a, the distance from magnetic pole portion 1 is small such that the eddy current becomes larger. As a result, the output from detecting coil 4 decreases. On the other hand, the following magnetic pole portion 2 on the left hand in the figure has a larger space between it and surface 3a wherein the eddy current is small such that detecting coil 5 generates a larger output. Consequently, the differential output from detecting coils 4 and 5 increases, for example, the output has a wave form including projecting portions A as shown in FIG. 10. Therefore, it is detected that surface 3a of metallic body 3 has convex portion 3b. 
In recent years, there has been a problem with forged foreign coins and counterfeit coins being frequently used with domestic vending machines and ticket machines.
Currently, the following means are employed solely or in combination to identify coins in vending machines, ticket machines and central processors depending on the required rate of identification:
1) a magnetic sensor detecting conductivity, mass, diameter and thickness of a metal piece as a difference in eddy current loss;
2) an optical sensor, such as a CCD, identifying the optical pattern of a coin; and
3) identifying the diameter and thickness by mechanically selecting the size.
The conventional apparatus as described above has a simple configuration and is able to provide reliable detection outputs. However, the wave form of the detection outputs may differ from the actual shape of the surface.
For example, as shown in FIG. 1, when the summit of convex portion 3b on the surface to be identified 3a of metallic body 3 has an extended flat plane, both magnetic pole portion for detection 1, which is positioned on the right side in the figure, and the other magnetic pole portion 2, which follows magnetic pole 1 from the left side, can face the flat portion of convex portion 3b simultaneously. As a result, the distances from each of magnetic poles 1 and 2 to the surface become identical. Therefore, the sensor does not provide a differential output from detecting coils 4 and 5 although convex portion 3b exists thereat. As shown in FIG. 2(b), the differential output is zero such that the convex portion 3b cannot be detected.
However, qualities of the forged foreign coins and counterfeit coins are improved every year. Therefore, it is very difficult to prevent illegal use of those coins by using simple identification parameters such as the material, diameter and/or thickness.
Also, simultaneously verifying a section of a coin for more accurate identification data is required instead of the conventional macro identification of material, diameter and/or thickness.
In a coin transferring apparatus, the position of coin 102 tends to move (e.g. by about 0.3 mm) while being transferred, i.e., when the coin is falling with rotation in a vending machine or when the coin is transferred on belt 103 in a central processor. Therefore, a magnetic sensor using eddy current loss cannot identify any coin 102 having a diameter which is different from the original coin 102 by an amount smaller than the amount of the change in position.
The above discussed fluctuations in the position of the coin are within the acceptable limit as long as only domestic coins are subject of identification. However, identification may be impossible in the case of foreign coins which are similar in material, diameter and thickness.
The present invention intends to provide a magnetic sensor, in particular a metallic surface identifying sensor which can precisely identify the shape of a surface of a metallic body while maintaining a simple configuration. Also, the present invention intends to provide a magnetic sensor which individually detects information about metallic bodies such as coins, e.g., material, thickness and diameter, such that is precisely identifies the kind of metallic body to be detected or weather the metallic is authentic.
It is another purpose of the present invention to provide a differential magnetism sensor apparatus which gives a high precision of the detection even if outputs from differential detecting coils have a phase shift and which can cope with a high magnetizing frequency without an expensive differential amplifier.
Another purpose of the present invention is to provide a coin identifying apparatus and a magnetic sensor body which identify the authenticity of coins by improving identifying performance using the characteristics of the coins.
Yet another purpose of the present invention is to provide a coin identifying sensor which can accurately detect the diameter of a coin in spite of a change in the position of the coin.
Another purpose of the present invention is to provide a coin identifying sensor which accurately detects the thickness of a coin regardless of a change in the position of the coin.
The present invention also intends to provide a proximity sensor which shows a high sensitivity due to a large variation of the output of the detection corresponding to a variation of the distance from an object to be detected and also shows a good linearity of the output of the detection.
Another purpose of the present invention is to provide a proximity sensor which shows a good temperature characteristic of the output of the detection, the shape of which is thin.
It has now been discovered that these purposes can be achieved by the present invention. In particular, the present invention provides for a metallic surface identifying sensor including a magnetic pole portion for detection, a reference magnetic pole portion, magnetizing coils and detecting coils. The magnetic pole portion shifts facing a surface of a magnetic body to be identified having an uneven shape wherein the distance from the surface to be identified changes along with the uneven shape while shifting. The reference magnetic pole portion is placed across from a reference surface, wherein the distance from the reference surface to the magnetic pole portion is maintained approximately constant regardless of the shifting of the magnetic pole portion for detection in relation with the surface to be identified. The magnetizing coils are separately wound around the magnetic pole portion for detection and the reference magnetic pole portion to generate magnetic fluxes. The detecting coils are separately wound around the magnetic pole portion for detection and the reference magnetic pole portion to detect the magnetic fluxes wherein said uneven shape of the surface to be identified of the metallic body is detected based on detection outputs from the magnetic pole portion.
The present invention provides for a differential magnetism sensor apparatus including a magnetizing coil which generates a closed loop magnetic field, a differential detecting coil which detects a variation of a magnetic flux passing through the magnetizing coil, and a differential amplifying device which amplifies a difference between two outputs from ends of the differential detecting coil and outputs the amplified difference as a differential output. The differential magnetism sensor apparatus further includes a demodulating device which demodulates each of the two outputs from the differential detecting coil and a low-pass filter which removes a high-frequency constituent from each of two outputs from the demodulating device, the two outputs from the differential detecting coil pass through the demodulating device and the low-pass filter and are input to the differential amplifying device.
In addition, the present invention provides for a coin identifying apparatus including a coin transferring path on which a coin to be detected is transferred along a guide while being held on a moving surface; a first detecting sensor which is positioned on the coin transferring path and which detects data regarding the material or the thickness of the coin; a second detecting sensor which detects data regarding the diameter of the coin; a third detecting sensor which detects at least one of the following: data regarding unevenness on the surface of the coin, data regarding unevenness on the side of the coin, and data regarding unevenness at the edge of the coin; and an identifying means which identifies the coin based on output signals from the first, second and third detecting sensors. The identifying means provides a temporary decision on the coin to be detected based on outputs from the first detecting sensor and the second detecting sensor and identifies the coin based on the output from the third detecting sensor while considering the temporary decision.
Furthermore, the present invention provides for a magnetic sensor body including a coin transferring path on which a coin to be detected is transferred along a guide while being held on a moving surface; a first detecting sensor which is positioned on the coin transferring path and which detects data regarding the material or the thickness of the coin; a second detecting sensor which detects data regarding the diameter of the coin; and a third detecting sensor which detects at least one of the following: data regarding unevenness on the surface of the coin, data regarding unevenness on the side of the coin, and data regarding unevenness at the edge of the coin. Furthermore, the magnetic sensor body identifies the coin by using the first, second and third detecting sensors which are integrated by a mold. Also, the first detecting sensor is configured such that it is shaped as a xe2x80x9cUxe2x80x9d, the coin transferring path is formed between two free ends, each of the free ends has a projecting portion which projects toward the coin transferring path, and a magnetizing coil and a detecting coil are wound around the projecting portion. The second detecting sensor is configured such that it is shaped as a xe2x80x9c] (U)xe2x80x9d, and the coin transferring path is formed between two free ends, and a magnetizing coil and a detecting coil are wound around a connecting portion which is positioned opposite from the free ends. The third detecting sensor is placed in the vicinity of the guide on the coin transferring path.
Also, the present invention provides for a magnetic sensor shaped as a xe2x80x9c] (U).xe2x80x9d This magnetic sensor has projecting portions such that two free ends face each other wherein a magnetizing coil and a detecting coil are wound around each of the projecting portions and a metallic body is detected while passing between the projecting portions.
In addition, the present invention provides for a magnetic sensor shaped as a xe2x80x9c] (U).xe2x80x9d This magnetic sensor has a magnetizing coil and a detecting coil wound around a connecting portion opposite from two free ends and a metallic body to be detected sandwiched between the two free ends.
Additionally, the present invention provides for a coin identifying sensor including first and second detecting sensor portions which detect data regarding the diameter on both sides of a coin transferred along a guide. The first and second detecting sensor portions are formed such that their cross sections are shaped as an xe2x80x9cExe2x80x9d. The free ends of the E-shaped first and second detecting sensor portions face each other. A magnetizing coil and first and second detecting coils are wound around the first and second detecting sensor portions. Further, the magnetizing coils of the first and second detecting sensor portions are connected in series while the first and second detecting coils are connected in phase. The first detecting coil and the second detecting coil are configured to be differential.
Further, the present invention provides for a coin identifying sensor including a first detecting sensor portion and a second detecting portion. The first detecting sensor portion has a detecting magnetic sensor including a cross section shaped as a xe2x80x9cUxe2x80x9d wherein a coin is transferred along a guide between free ends of the U-shaped detecting magnetic sensor, and a reference magnetic sensor which has a shape identical to the detecting magnetic sensor. The first detecting sensor portion detects data regarding the diameter on one side of the coin transferred along the guide. The second detecting sensor portion is configured identical to the first detecting sensor portion and is placed such that free ends of the detecting magnetic sensors of the first and second detecting sensor portions face each other wherein the second detecting sensor portion detects data regarding the diameter on the other side of the coin. A magnetizing coil and first and second detecting coils are wound around the first and second detecting sensor portions. The magnetizing coil of the first and second detecting sensor portions are connected in series while the first and second detecting coils are connected in phase. The first detecting coil and the second detecting coil are configured to be differential.
The present invention also provides for a coin identifying sensor including first and second thickness detecting sensor portions placed at both ends of a coin transferred along a guide wherein each of the first and second thickness detecting sensor portions include a combination of sensor bodies having a xe2x80x9c] (U)xe2x80x9d-shaped cross section. The first thickness detecting sensor portion is placed in the vicinity of one side of the coin in the thickness direction while the second thickness detecting sensor portion is placed in the vicinity of the other side of the coin. Also, magnetizing coils and first and second detecting coils are wound around the first and second thickness detecting sensor portions. Further, the magnetizing coils of the first and second thickness are connected in series and the first detecting coil and the second detecting coil are connected in phase and are configured to be differential.
In addition, the present invention provides for a displacement sensor which provides stable detection results with high detection sensitivity by using a simple configuration. More specifically, the displacement sensor has a configuration in which an output changes corresponding to a change in the relative position to an object to be detected and which detects a proximity position in relation to the object to be detected based on the change in the output. Magnetizing coils and detecting coils are wound around a core body such that they are lined on the axis of the core body. Furthermore, one end of each of the magnetizing coils and the detecting coils are placed at a core center portion at the approximate center of the core body in the axial direction while the other ends of the magnetizing coils and detecting coils are placed at a pair of core end portions at each end of the core body in the axial direction. Also, the axial direction of the core body is arranged to be approximately equal to the direction of a change in the relative position in relation to the object to be detected such that one of the core end portions and the object to be detected face each other when the object to be detected approaches and retreats from the core end portion.
Finally, the present invention provides for a proximity sensor which detects the location of an object to be detected without touching the object. The proximity sensor includes two magnetizing portions each of which includes a magnetizing core and a magnetizing coil wound around the magnetizing core and which are disposed at a predetermined interval, and a magnetism detecting portion which includes a detecting core and a detecting coil wounded around the detecting core and which is disposed between the two magnetizing portions. The two magnetic portions generate a flux path which passes the object to be detected and a flux path which passes the magnetism detecting portion. Also, the variation of the magnetic flux of the flux path which passes the object to be detected corresponding to a variation of the location of the object to be detected varies the magnetic flux of the flux path which passes the magnetism detecting portion, and the location of the object to be detected is detected by means of a variation of the output of the detection from the magnetism detecting portion.